The present invention relates to a method and a portable apparatus for measuring a radiation dose, and in particular relates to identifying the radionuclide source of the radiation.
Conventional radiation dose measuring devices include Geiger Mueller (GM) tube devices, which utilize gas amplification of ion pairs generated along a locus of radiation to produce an electric pulse, and scintillation type devices, which utilize photomultiplier tubes which react to photons generated by radiation incident upon a scintillation screen to produce an electric pulse. Photomultipliers perform multi-step amplification of photoelectrons emitted from a photocathode by making the photoelectrons cascade through secondary emission electrodes.
In measuring and accurately determining the various peaks in a .gamma.-ray spectrum or in identifying a radionuclide by using a radiation detecting device, it is necessary to calibrate the pulse amplitude scale to the absolute energy of the .gamma.-ray. Because conventional correction methods utilize a radiation source, the above-described measurements may not be done in places where radiation sources are prohibited or restricted. There is an increasing need to measure radiation doses and identify the radiation source nuclides in water, air, rainwater, soil, agricultural products, marine products, and other industrial and environmental areas, especially as a result of recent radioactive pollution in some countries resulting from nuclear power plant accidents. In some situations such measurements are not readily performed because the use of radiation sources in residential areas is restricted, and usually it is difficult to obtain a radiation source even when the use is permitted.